1. Field of the Invention
The present invention relates to a method and apparatus of lifting an object, such as a metal block, and more particularly to such an apparatus adapted to lift a block having a threaded socket of a predetermined diameter formed therein for attachment to a lifting device.
2. Background Art
In a manufacturing operation, quite often when metal is to be machined into a particular configuration, the metal to be machined is provided in the form of a block (many times in the configuration of a rectangular prism). Since such blocks can each weigh several hundred pounds or more, it is necessary to provide some convenient means for lifting these blocks, and this is commonly done by forming in the block a threaded socket of a predetermined diameter. To lift the block, there is provided a connecting device in the form of a lift ring. The lift ring is commonly made in the form of a loop that is adapted to be connected to the hook of a crane, and attached to this loop is a threaded stud which can be threaded into the lifting socket of the block.
Normally, the person who is arranging for the block to be lifted selects a lifting ring having a threaded stud with a diameter matching that of the socket in the block. The stud is threaded into the socket so that the lift ring is properly secured to the object. Then the lifting operation can be accomplished quite simply by connecting the crane's hook to the loop of the lift ring.
For many years, one of the problems in conducting this operation is that the lifting sockets formed in the block are of different diameters. For example, if the block is somewhat heavier, the socket may be made somewhat larger to accommodate a larger threaded stud. If this person happens to select a ring having a stud of the wrong diameter, it sometimes happens that he tries to force the threaded stud of the wrong size into the socket, in the hopes that there will be sufficient engagement to accomplish the lifting action. Also, it sometimes happens that the lift ring having the stud of the appropriate size has been mislaid or is otherwise not available. Rather than delay lifting the block entirely, or using some other method of lifting the block, a lift ring with a stud of the wrong size is sometimes used as a poor compromise.
One of the problems in this improper matching of the threaded stud and socket is that threads on the stud of the lift ring become damaged, making it more difficult to use the lift ring in situations where the threaded stud does match the socket. This further complicates matters in that the person selecting the particular lift ring is not always sure whether a ring with a stud of the wrong diameter has been selected or whether the threaded stud, even though of the proper size, is difficult to thread into the socket because the threads are damaged to some extent.
The net result is that an improper connection is sometimes made between the lift ring and the object to be lifted. In a manufacturing operation, this can be a potential safety hazard. To the best knowledge of the applicant, the problems inherent in this lifting operation have existed many years. The prior art approaches to alleviate this problem have been, to the best knowledge of the applicant, precautionary, such as insuring that lift rings having the studs of the proper size are readily available. Further, reminders and warnings to the workers are placed in the work area that they should be careful that the attachment of the lift ring is properly made prior to lifting. However, in spite of the many precautions taken in manufacturing operations, the state of the art relative to the mechanics of lifting such blocks has not advanced to a state where this hazard could be substantially alleviated.
A search of the U.S. patent literature has turned up substantially nothing of any real relevance to the problems noted above, and U.S. Pat. No. 2,339,594, Goldberg et al, was the only patent cited in the report of the search conducted. This patent shows an adjustable pipe hanger where pipes of different size can be held in the hanger. Clamping bars having different arcuate configurations are provided to accommodate pipes of different diameter.
Accordingly, it is an object of the present invention to provide a method and apparatus to alleviate at least to some extent the problems noted above. It is a further object to provide a lift ring apparatus which can be used conveniently and effectively, and which provides for a more efficient operation, in addition to enhancing the safety of the operation.